. >> that was president obama last week. in fact one thing that both right and left agree on is that social and economic mobility, bowing able to make it no matter where you start from, is at the heart of the american dream. in recent years the most depressing statistics about this country have been that that mobility has declined, particularly compared with other countries, despite the anecdotes and celebrated examples, most americans appear to be stuck in the economic strata into which they were born. last week the most detailed study on this topic was released. it provides lots of fascinating clo clues about the causes of our problem, breaking american mobility down by geography. for example, if you were born in a detroit family in the bottom fifth of the income levels, you would have a 5% chance of making it to the top fifth. but if you were born in san diego, your chances are twice as good. why? we're going to get to the bottom of this. raj chetty is one of the authors of the study. he is an economist at harvard and won